[1]}
have shown that equalised odds, as well as all parity based notions,
is subject to the problem of infra-marginality
as a unified classification threshold is not sensible
if the underlying risk distributions are unequal for two demographic groups.
In such cases, the error scores will differ and parity cannot be achieved.
Furthermore,
equalised odds is usually only satisfiable when different classification
thresholds for the demographic groups are employed in the first place [2]}, [3]}.
In such cases, the use of the protected attribute is needed at classification
time,
which might not everywhere be legally feasible.
However,
[4]} argue that APP systems such as dropout detection
should include protected attributes,
albeit the authors only report a limited benefit in terms of
fairness and performance.
